Check with your local electrician or elect supply store , ask for a exterior motor base cover it looks like an reversed recepticle cover . drill the appropriate size hole in an exterior wall and flush mount the unit . when you lift the lid you will see the male prongs inside
, just plug you extension cord into the motor base .
I have mine wired into a power convertor/batt charger from a motor home so i can have multiple fused 12v
circuits and 110/120v circuits that are protected .
this part may only be avail to a liscenced electrician depending on your local codes .